This invention relates to electronics in general and in particular to liquid crystal displays.
The advent of liquid crystal display technology has had a profound effect in all areas of electronics, particularly the consumer area and in advanced instrumentation. The cost advantages of a solid state liquid crystal display (LCD) as well as the durability, when compared to mechanical counter-type displays or other technologies such as cathode ray tube displays, is well known.
The twisted nematic liquid crystal display has found particularly wide use in consumer applications due to its extremely low cost. However, dichroic "guest-host" displays are more useful in critical applications such as precision instrumentation and avionics since the viewing angle of a dichroic display is a significant improvement over that of a twisted nematic type display.
A significant problem with the use of dichroic liquid crystal displays has been the maintenance of a constant contrast ratio over widely varying lighting conditions, such as strong sunlight in a first instance compared to extremely dim back lit or front lit conditions at night. This problem has prevented wide-spread acceptance of dichroic liquid crystal displays in avionics applications where visual contrast and "readability" of the display is paramount under virtually all potentially encountered lighting conditions.